A new completion of Mozart's ZaÇde, which has come down to us with all of its dialogue and some instrumental interludes missing, makes its U.S. debut tonight as one of the centerpieces of Lincoln Center's 2006 Mostly Mozart Festival.

Mozart wrote ZaÇde when he was just 23, but put it aside when the commission for Idomeneo (to be performed at Mostly Mozart, as it happens, by William Christie and Les Arts Florissants on August 23 and 25) came along. He never returned to finish the work.

ZaÇde was conceived as a Singspiel — that is, a light-hearted quasi-operetta (just like The Magic Flute) combining skilled singing with spoken dialogue — depicting the rescue of enslaved Europeans and the enlightenment of the dastardly Turkish sultan who enslaved them.

But that's not how we'll see ZaÇde this week. Director Peter Sellars, striving as always for contemporary relevance, has taken the opportunity to make the work into a protest against the modern-day persistence of slavery. Though many of us in comfortable North America don't realize it, slavery does still exist in some parts of the world — under the radar of the law, as in sex trafficking, and legally in a few countries (who would rather not discuss the issue). There is also the issue of forced, low-wage-or-no-wage labor in sweatshops, one of which is the setting for Sellars's re-imagining of ZaÇde. The production reportedly opens with a speech about modern slavery, and to underscore the racial issues that are inevitably intertwined with this topic, the male roles have all been cast with African-American artists and the title role is sung by an Asian-American soprano.

Mozart's ZaÇde, in a new staging by Peter Sellars, opens tonight at 8 pm at the Rose Theater in the Jazz at Lincoln Center complex in the Time-Warner Center in Manhattan. Hyunah Yu sings the title role, with Norman Shankle, Russell Thomas, Alfred Walker and Terry Cook; in the pit, Mostly Mozart Festival music director Louis Langr_e conducts the period-instrument ensemble Concerto K‹ln. There are two further performances on Friday and Saturday, August 11 and 12, at 7 pm. Information and tickets are available at www.lincolncenter.org.